Hydrogen sulfide (H2S) is commonly found in natural gas wells and may also be produced in oil refining or other industrial processes. Because hydrogen sulfide increases corrosion and may be toxic in sufficient quantities, hydrogen sulfide content should be reduced to appropriate levels. An accepted method of reducing hydrogen sulfide content is the oxidation of hydrogen sulfide to sulfur and water. The sulfur product is considered benign in comparison to alternatives such as sulfur dioxide (SO2), the product of burning hydrogen sulfide and a precursor to acid rain.
The Claus process is the state-of-the-art process for oxidizing hydrogen sulfide to convert it to sulfur and water. The Claus process is a two-step process. In the first step, a large quantity of the elemental sulfur is recovered in a furnace, and about one third of the remaining H2S is oxidized to SO2. In the second step, the remaining H2S and the SO2 are reacted in a Claus reactor to form sulfur according to the reaction:2H2S+SO2→2H2O+3SUnfortunately, the gas fed to the Claus process must have a relatively high concentration of H2S gas to be efficiently incinerated in the furnace step. Also, the gas treated in a Claus process must have low amounts of hydrocarbons, which can interfere with the Claus reaction and generate other sulfur species, such as COS and CS2. As a result, an H2S-containing gas typically must be treated in an amine unit to first separate and concentrate the H2S. Thus, the Claus process is generally economical only for large scale operations.
Direct oxidation catalysts that promote the oxidation of H2S to sulfur and water in a single step are one alternative to the multistep Claus process. Direct oxidation is effective at lower concentrations of H2S. So, H2S separation in an amine unit is not necessary. Despite its advantages over the Claus process, direct oxidation is rarely used because the catalyst life is too short and attempts to regenerate the catalyst have failed.
Accordingly, there exists a need for a system and method for effectively regenerating the direct oxidation catalysts.